1. Field of the Invention
The invention relates to a method for the fabrication of at least one magnetic recording/reading head from a magnetic substrate.
2. Description of the Prior Art
A magnetic reading and/or recording head is formed by a ring-shaped magnetic circuit cut by a narrow gap consisting of a non-magnetic material.
Magnetic heads can be classified under three major groups:
massive heads are made by machining and joining two semi-heads, made of magnetic material, such as video heads (VHS heads) or analog audio heads. The coiling of these heads is done at the end of the fabrication method;
thin layer heads are made by successive deposition of magnetic, dielectrical and conductive materials. These layers undergo masking and etching operations which enable the magnetic circuit, the gap and the conductive turns to be obtained;
heads having, on either side of the gap, a magnetic metallic alloy with a thickness that varies between 0.1 and 40 micrometers, the rest of the magnetic circuit and the conductive turns being made in the same way as for the massive heads. These are so-called MIG (metal in gap) heads which are used today in 8 mm. or RDAT (rotary digital audio tape) systems.
In the method of fabrication of a magnetic recording/reading head, it is often necessary to machine a heterogeneous part, formed by the association of a magnetic material (ferrite for example) and a non-magnetic material (glass for example). This is the case, notably, for the fabrication of the magnetic head described in the French patent application by the present applicant, filed under No. 87 14824. If a magnetic thin layer has to be deposited on this machined head, as for the magnetic head described in the French patent application by the present applicant, filed under No. 87 14820, it is necessary to have an excellent surface quality.
However, grinding a heterogeneous part always results in a different degree of wear on the two materials forming this heterogeneous part. This difference in wear is all the greater when the materials have different hardnesses. This is particularly so in the case of ferrite which is usually ground with a mixture of diamond powder, and of glass which is usually ground with cerium oxide. The plane thus machined therefore has a planar surface defect which may be incompatible with the requirements of additional steps for making the magnetic head.
To overcome this problem, the invention proposes a new method for the fabrication of at least one magnetic recording/reading head which enables the grinding, at different stages, of the magnetic and non-magnetic materials forming the active face of the head.